This application proposes to study Chlamydia trachomatis infection in a new experimental monkey model (subcutaneous model) in which monkeys are inoculated with the organisms into subcutaneous homografts of oviductal tissues. The objectives are to elucidate the immunopathology of C. trachomatis salpingitis and the pathogenesis of its sequela, tubal infertility, and to evaluate the immunity against infection and the prevention of infection by immunization. The specific aims are 1) to define the clinical course of infection by cell culture isolation of the organisms, detection of chlamydial antigens in tissue by immunofluorescence and immunoperoxidase stains, measurement of serum antibody response by the indirect immunofluorescent antibody test, and histopathological electron microscopic study of tissue biopsy, 2) to observe the effect of female sex hormones on the susceptibility of the fallopian tissue to infection and the course of infection by timing the inoculation to the estrogen or progesterone phase in the animals artificially cycled with hormone implant after oophorectomy, 3) to determine whether monkeys recovered from the primary infection will develop resistance against rechallenge inoculation, 4) to study the pathogenesis of tubal infertility by analyzing the histopathological changes of inflammatory response with the tissue sections stained with Hematoxylin & Eosin stain for routine histology and with immunofluorescence and immunoperoxidase stains for detection of chlamydial antigens and identification of infiltrating lymphocyte subclasses, 5) to assess the immunity, both acquired after infection and induced by immunization, and its specificity by homologous and heterologous rechallenge inoculation, and 6) to evaluate the effectiveness and deleterious effect of vaccine by immunization with purified formalin inactivated whole organism vaccine or fractionated antigen vaccine.